linux-kernel - Re: Bloatwatch 2.6.28-rc1: last_sysfs

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Message-ID: <4902F710.3020100@redhat.com>
Date:	Sat, 25 Oct 2008 06:38:08 -0400
From:	Chris Snook <csnook@...hat.com>
To:	Matt Mackall <mpm@...enic.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	akpm <akpm@...uxfoundation.org>
Subject: Re: Bloatwatch 2.6.28-rc1: last_sysfs_file

Matt Mackall wrote:
> On Fri, 2008-10-24 at 15:52 -0500, Matt Mackall wrote:
>> 2.6.28-rc1 adds 4k for last_sysfs_file debug tracking. That's one hell
>> of a long sysfs path.
>>
>> http://www.selenic.com/bloatwatch/?cmd=compare;v1=2.6.27;v2=2.6.28-rc1;part=/built-in/fs/sysfs
> 
> ..especially given that printk is limited to 1k at a time.
> 
> 
> sysfs: shrink last_sysfs_file to a reasonable size
> 
> sysfs was reserving 4k to store filenames for debug despite printk being
> limited to 1k. Shrink this to something more reasonable.
> 
> Signed-off-by: Matt Mackall <mpm@...enic.com>
> 
> diff -r ac8c82ff3be7 fs/sysfs/file.c
> --- a/fs/sysfs/file.c	Fri Oct 24 13:13:04 2008 -0500
> +++ b/fs/sysfs/file.c	Fri Oct 24 16:11:53 2008 -0500
> @@ -25,7 +25,7 @@
>  #include "sysfs.h"
>  
>  /* used in crash dumps to help with debugging */
> -static char last_sysfs_file[PATH_MAX];
> +static char last_sysfs_file[200]; /* allow for disgustingly long paths */
>  void sysfs_printk_last_file(void)
>  {
>  	printk(KERN_EMERG "last sysfs file: %s\n", last_sysfs_file);
> 
> 

Please don't use magic numbers.  Use a symbolic constant, and modify printk.c to 
use the same.  If we're going to impose limits lower than the maximum, let's at 
least be consistent about it.

-- Chris
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